1. Field of the Invention
This invention relates to a silicone rubber/epoxy resin integral composite and more particularly, an integral composite comprising an organic peroxide-cured or addition reaction-cured silicone rubber firmly integrated with a cured epoxy resin useful in electric and electronic parts, business machines, automobiles, and precision equipment. It also relates to a method for preparing such an integral composite.
2. Prior Art
In the recent years, silicone rubbers have been expanding their application in the fields of electric and electronic parts, business machines, and automobiles because they are acknowledged highly reliable with respect to heat resistance, weather resistance, and electric properties. On the other hand, epoxy resins which are thermosetting resins also find a wide variety of applications because of excellent electrical and mechanical properties and adhesion. It is thus desired to have a composite of silicone rubber and epoxy resin. There is a need for integral molded parts wherein the two components are firmly joined.
A number of attempts have been made for joining silicone rubber and organic resins together. For example, (1) a molded resin on the surface is coated with a primer and a curable silicone rubber is applied thereon and cured. (2) A self-adhesive silicone rubber material is cured to a molded resin. (Note that there are available a number of patents relating to self-adhesive silicone rubber compositions, especially adhesive components thereof.) (3) An organopolysiloxane containing more than 30 mol % of a hydrogen atom directly attached to a silicon atom is added to an organic resin which is joined to an addition curing type silicone rubber (see U.S. Pat. No. 4,582,762, U.S. Pat. No. 4,686,124, U.S. Pat. No. 4,814,231 and U.S. Pat. No. 4,834,721 corresponding to JP-B 34311/1990). (4) A silicone rubber is physically fitted in an organic resin (see JP-B 45292/1988). (5) A silicone rubber is integrally joined to an olefin resin having grafted thereto a compound having an aliphatic unsaturated group and a hydrolyzable group attached to a silicon atom (see EP 276790A corresponding to JP-A 183843/1988).
However, method (1) using a primer is cumbersome in that a resin molding must be taken out of a mold before a primer can be applied. Method (2) of curing a self-adhesive silicone rubber material to a molded resin has the serious problem that when the silicone rubber-coated resin is molded in a mold, the silicone rubber itself adheres to the mold. Method (3) of adding an organopolysiloxane to a resin has the problem that it is difficult for the resin to exert its inherent properties because the properties of the resin itself can be altered by the siloxane added thereto. Method (4) has a likelihood that physical engagement be disrupted by physical forces. Method (5) requires a primer for the integration of an addition curing type silicone rubber.